The conventional liquid crystal display (LCD) backlight module not only has light emitting diode (LED) as the light source, but also has light-guide panel, diffuser plate, prism sheet, reflector, and some other components. The manufacturers have already been developing a type of optical film with several prism bars disposed on the substrate and also integrating two optical films into one in order to achieve a thinner design on the film. When this type of optical films is to combine with other components to form an optical film assembly, connecting adhesive is usually used to connect the components. One side of the connecting adhesive connects with the prism bars of one optical film, and the other side of the connecting adhesive connects with the substrate of another optical film. Some optical equipments may adjust the effect of the light with this optical film assembly.
However, the backlight module of the LCD tends to generate heat during its operation, and the optical film assembly is then heated by the heat. Since the coefficient of thermal expansion (CTE) of the connecting adhesive and those of the different layers of the optical films are different, the change of temperature may cause deformation on the prism bars of the optical film because of the change of tension from the connecting adhesive, thereby affecting the light effect of the optical film and causing the light to be inaccurate.